Laser annealing systems and methods with ultra-short dwell times

ABSTRACT

Laser annealing systems and methods for annealing a semiconductor wafer with ultra-short dwell times are disclosed. The laser annealing systems can include one or two laser beams that at least partially overlap. One of the laser beams is a pre-heat laser beam and the other laser beam is the annealing laser beam. The annealing laser beam scans sufficiently fast so that the dwell time is in the range from about 1 μs to about 100 μs. These ultra-short dwell times are useful for annealing product wafers formed from thin device wafers because they prevent the device side of the device wafer from being damaged by heating during the annealing process. Embodiments of single-laser-beam annealing systems and methods are also disclosed.

CLAIM OF PRIORITY

This application is a divisional application of U.S. patent applicationSer. No. 13/909,542, filed on Jun. 4, 2013, and which is incorporated byreference herein and which claims the benefit of priority under 35U.S.C. §119(e) of U.S. Provisional Application Ser. No. 61/658,086,filed on Jun. 11, 2012, which is incorporated herein by reference.

FIELD

The present disclosure relates generally to laser annealing ofsemiconductor materials when forming integrated circuit structures, andin particular relates to systems for and methods of ultra-short laserannealing having a relatively high degree of temperature uniformity.

BACKGROUND ART

There are a variety of applications that require the use of a line imagehaving a relatively uniform intensity. One such application is laserthermal processing (LTP), also referred to in the art as laser spikeannealing (LSA), or just “laser annealing.” Laser annealing is used insemiconductor manufacturing for a variety of applications, including foractivating dopants in select regions of devices (structures) formed in asemiconductor wafer when forming active microcircuits such astransistors and related types of semiconductor features.

One type of laser annealing uses a scanned line image from a light beamto heat the surface of the wafer to a temperature (the “annealingtemperature”) for a time long enough to activate the dopants in thesemiconductor structures (e.g., source and drain regions) but shortenough to prevent substantial dopant diffusion. The time that the wafersurface is at the annealing temperature is determined by the powerdensity of the line image, as well as by the line-image width divided bythe velocity at which the line image is scanned (the “scan velocity”).

To achieve high wafer throughput in a commercial laser annealing system,the line image should be as long as possible, while also having a highpower density. An example range for usable line-image dimensions is 5 mmto 100 mm in length (cross-scan direction) and 25 microns to 500 micronsin width (scan direction), with typical dimensions being 10 mm long by100 microns wide. To achieve uniform annealing, it is also necessary forthe intensity profile along the line-image length to be as uniform aspossible, while non-uniformities along the line-image width are averagedout during the scanning process.

Typical semiconductor processing requirements call for the annealingtemperature to be between 1000° C. and 1300° C., with a temperatureuniformity of +/−3° C. To achieve this degree of temperature uniformity,the line image formed by the annealing light beam needs to have arelatively uniform intensity in the cross-scan direction, which undermost conditions is within +/−5%.

Typical semiconductor applications require an annealing time of 0.1milliseconds to 10 milliseconds (ms). To meet this requirement, amechanical stage can be used to move the wafer perpendicular to the longdimension of the beam. With a stage velocity of 100 mm/sec and a shortbeam width of 100 microns, the thermal annealing (dwell) time is 1 ms.

Unfortunately, for certain semiconductor device fabrication situations,the annealing temperature and annealing time are constrained by otherfactors, such as wafer thickness and the type of semiconductor devicestructures formed on the wafer. In such situations, the conventionalannealing (dwell) times provided by conventional laser annealing systemsare unsuitable.

SUMMARY

Laser annealing systems and methods for annealing a wafer withultra-short dwell times are disclosed. The laser annealing systems caninclude one or two laser beams that at least partially overlap. One ofthe laser beams is a pre-heat laser beam and the other laser beam is theannealing laser beam. The annealing laser beam scans sufficiently fastso that the dwell time is in the range from about 1 μs to about 100 μs.These ultra-short dwell times are useful for annealing product wafersformed from thin device wafers because they prevent the device side ofthe device wafer from being damaged by heating during the annealingprocess. Embodiments of single-laser-beam annealing systems and methodsare also disclosed.

A first aspect of the disclosure is an ultra-fast laser annealing systemfor annealing a semiconductor wafer having a wafer surface. Theultra-fast laser annealing system includes a primary laser system, asecondary laser system. The primary laser system forms a primary imageon the wafer surface at a first wavelength. The primary image increasesan amount of absorption of light at a second wavelength. The secondarylaser system forms a secondary image on the wafer surface at the secondwavelength. The secondary image resides at least partially within theprimary image. The secondary laser system includes a scanning opticalsystem that scans the secondary image over the wafer surface with adwell time of between 1 μs and 100 μs. That causes the wafer surface toreach a peak annealing temperature T_(AP) between 350° C. and 1250° C.

The ultra-fast laser annealing system preferably further includes athermal emission detector system, a collection optical system, a powersensor and a controller. The thermal emission detector system isoperably arranged to detect thermal emission radiation from the wafersurface at the location of the secondary image and generate anelectrical thermal emission signal. The collection optical system isoperably arranged to collect reflected light from the secondary laserbeam that reflects from the wafer surface at the location of thesecondary image and generate an electrical reflected light signal. Thepower sensor is arranged to measure an amount of power in the secondarylaser beam and generate an electrical power signal representativethereof. The controller is operably connected to the thermal emissiondetector system, the collection optical system, the power sensor and thesecondary laser system. The controller is configured to receive andprocess the electrical thermal emission signal, the electrical powersignal and the electrical reflected light signal and determine a wafersurface temperature T_(S) at the location of the secondary image.

In the ultra-fast laser annealing system, the thermal emission detectorsystem and the scanning optical system preferably include overlappingoptical path sections.

In the ultra-fast laser annealing system, the controller is preferablyconfigured to control an amount of power in the secondary laser beambased on the measured wafer surface temperature T_(S).

In the ultra-fast laser annealing system, the primary and secondaryimages preferably generate a peak annealing temperature that does notvary over the semiconductor wafer by more than +/−3° C.

In the ultra-fast laser annealing system, the scanning optical systempreferably includes a scanning mirror operably connected to a mirrordriver. The mirror driver is operably connected to and controlled by thecontroller.

In the ultra-fast laser annealing system, the first wavelength ispreferably in the range from 300 nm to 650 nm.

In the ultra-fast laser annealing system, the second wavelength ispreferably in the range from 500 nm to 10.6 microns.

In the ultra-fast laser annealing system, the secondary laser systempreferably includes a fiber laser having an output power of between 50watts and 5000 watts.

In the ultra-fast laser annealing system, the semiconductor waferpreferably includes a device wafer having thickness in a range: a) from10 μm to 100 μm, or b) from 500 μm to 1,000 μm.

A second aspect of the disclosure is a method of annealing asemiconductor wafer having a wafer surface. The method includes forminga primary image on the wafer surface at a first wavelength. The primaryimage increases an amount of absorption of light at a second wavelength.The method also includes forming a secondary image on the wafer surfaceat the second wavelength. The secondary image resides at least partiallywithin the primary image. The method also includes scanning thesecondary image over the wafer surface with a dwell time of between 1 μsand 100 μs and that causes the wafer surface to reach a peak annealingtemperature T_(AP) between 350° C. and 1250° C.

In the method, the first wavelength is preferably in the range from 300nm to 650 nm.

In the method, the second wavelength is preferably in the range from 500nm to 10.6 microns.

The method preferably further includes measuring a wafer surfacetemperature T_(S) at the location of the scanned secondary image. Themethod also preferably further includes controlling an amount of powerin the secondary laser beam for forming the secondary image in order tokeep the peak annealing temperature T_(AP) to within +/−3° C.

In the method, measuring the wafer surface temperature T_(S) preferablyincludes measuring an amount of power in the secondary laser beam.Measuring the wafer surface temperature T_(S) also preferably includesmeasuring an amount of thermal radiation emitted from the location ofthe scanned secondary image. Measuring the wafer surface temperatureT_(S) also preferably includes measuring an amount of reflected lightfrom the location of the secondary image caused by reflection of thesecondary light beam. Measuring the wafer surface temperature T_(S) alsopreferably includes calculating the wafer surface temperature T_(S)using a look up table obtained from a calibration process.

A third aspect of the disclosure is an ultra-fast laser annealing systemfor annealing a semiconductor wafer having an annealing surface. Theultra-fast laser annealing system includes a laser and a scanningoptical system. The laser generates a laser beam having an annealingwavelength in the range from about 300 nm to about 650 nm. The scanningoptical system receives the laser beam and scans the laser beam age overthe annealing surface as a scanned image having a dwell time of between1 μs and 100 μs. That causes the annealing surface to reach a peakannealing temperature T_(AP) between 350° C. and 1250° C.

In the ultra-fast laser annealing system, the semiconductor wafer ispreferably a product wafer formed from a device wafer and a carrierwafer. The device wafer defines the annealing surface and has athickness in the range from about 10 μm to about 100 μm.

In the ultra-fast laser annealing system, the scanning optical system ispreferably configured as an F-theta scanning system.

A fourth aspect of the disclosure is a method of annealing asemiconductor wafer having an annealing surface. The method includesforming an image on the annealing surface using a laser beam having awavelength in the range from about 300 μm to about 650 μm. The methodalso includes scanning the image over the annealing surface with a dwelltime of between 1 μs and 100 μs. That causes the annealing surface toreach a peak annealing temperature T_(AP) between 350° C. and 1250° C.

In the method, the semiconductor wafer is preferably a product waferformed from a device wafer and a carrier wafer. The device wafer definesthe annealing surface and has a thickness in the range from about 10 μmto about 100 μm.

In the method, scanning the image is preferably performing using anF-theta scanning optical system.

A fifth aspect of the disclosure is a method of annealing a photoresistlayer supported by a surface of a semiconductor wafer. The methodincludes forming an image on the surface of the semiconductor waferusing a laser beam having a wavelength in the range from about 300 nm toabout 1000 nm. The method also includes scanning the image over thesurface of the semiconductor wafer with a dwell time of between 100 μsand 1 ms. That causes the photoresist layer to reach a peak annealingtemperature T_(AP) between about 300° C. and about 400° C.

In the method, the laser beam and semiconductor wafer preferably definea thermal diffusion length L_(DIFF) and an associated optical absorptiondepth D_(AD) in the semiconductor wafer. The image scanning is carriedout such that D_(AD)<L_(DIFF).

All references cited herein are incorporated by reference herein.

The claims as set forth below are incorporated into and constitute partof the Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1D are various views of example wafers that can besubject to laser annealing using the dual-beam ultra-fast laserannealing systems and methods of the present disclosure;

FIG. 2 is a plot of the annealing time t_(A) (μs) versus the diffusionlength L_(DIFF) (μm) for bulk silicon;

FIG. 3 plots the optical absorption depth D_(AD) (μm) versus the wafersurface temperature T_(S) (° C.) for wavelengths λ=1.06 μm, 0.98 μm and0.53 μm;

FIG. 4 is a schematic diagram of an example dual-beam ultra-fast laserannealing system;

FIGS. 5A through 5E are schematic diagrams that illustrate exampleembodiments of the relative sizes and orientations of the primary andsecondary images formed on the wafer surface by the dual-beam ultra-fastlaser annealing system of FIG. 1;

FIG. 6 is another schematic diagram of an example dual-beam ultra-fastlaser annealing system that includes more details of the thermalemission detection system incorporated therein;

FIG. 7 is a close-up view of an example collection optical system usedto collect reflected light from the wafer surface from the secondarylaser beam;

FIGS. 8A through 8C illustrate an example embodiment of a scanningoptical system that has an F-theta configuration and illustrates how thescanning optical system scans the secondary laser beam and the secondaryimage from one edge of the wafer to the other;

FIG. 9 is a view of the scanning optical system of FIGS. 8A through 8Cfrom another direction and shows how the scanning optical system can beconfigured so that the secondary laser beam has an incident angle thatis substantially the Brewster angle for silicon;

FIG. 10A is similar to FIG. 6 and illustrates an example embodiment of alaser annealing system that includes a single rapidly scanned laserbeam; and

FIG. 10B is similar to FIG. 10A and illustrates an example embodimentwherein the scanning secondary laser beam from the secondary lasersystem is used to anneal a layer of photoresist supported on the wafersurface.

DETAILED DESCRIPTION

Reference is now made in detail to embodiments of the disclosure,examples of which are illustrated in the accompanying drawings. Wheneverpossible, the same or like reference numbers and symbols are usedthroughout the drawings to refer to the same or like parts.

The fabrication of certain types of semiconductor devices, such as imagesensors and high-power devices, involves the use of relatively thinsemiconductor wafers. FIG. 1A is an example side view of a product wafer10 having a top side 21 that defines a top surface 22 and a back side 23that defines a back surface 24.

FIG. 1B illustrates the formation of an example product wafer 10 formedby interfacing a device wafer 10 a and a carrier wafer 10 b. The devicewafer 10 a has a front side 12 a in which devices are formed and is alsocalled the device side, and an opposite back side 14 a. The carrierwafer 10 b has a front side 12 b on which an oxide layer 15 is formed,and an opposite back side 14 b. The resulting wafer 10, referred toherein as a product wafer, is formed interfacing the device side 12 a ofthe device wafer 10 a with the front side 12 b of the carrier wafer 10b. The oxide layer 15 serves as a bonding layer that bonds the twowafers 10 a and 10 b together. Thus, the front side 12 b of the carrierwafer 10 b is also called the bonding side. The resulting product wafer10 is shown in FIG. 1C. At this point, the device wafer 10 a is grounddown from the back side 14 a to reduce the thickness of the device wafer10 a from about 750 μm to a thickness TH in the range from about 10 μmto about 100 μm, as shown in the close-up inset of FIG. 1C.

FIG. 1D is similar to FIG. 1C and includes an inset that shows a moredetailed close-up cross-sectional view of an example structure 30 of theproduct wafer 10. The example structure 30 is in the form of a CMOSsensor. The carrier wafer 10 b with the oxide layer 15 (which is about 4μm thick) supports the device wafer 10 a, which includes metallizationfeatures 34 (e.g., lines) that extend into the oxide layer 15. Themetallization features 34 make contact with an adjacent CMOS devicelayer 40. The CMOS device layer 40 is in turn supported by the thinneddevice wafer 10 a, which as mentioned above has a thickness TH in therange from about 10 μm to 100 μm. In another example, the thickness THis in the range from about 500 μm to about 1,000 μm.

A thin ion-implant layer 44 that needs to be laser annealed is formed inthe thinned device wafer 10 a adjacent its back side 14 a, which definesthe top surface 22. The annealing of thin ion-implant layer 44 serves tomake the ion-implant layer 44 conducting, which in turn allows it toserve as an electrical contact layer.

In the example CMOS device structure 30, the electronic features of theCMOS device reside from about 10 μm to about 100 μm away from the backside 14 a, which is usually not patterned. Thus, in an example back side14 a of the device wafer 10 a defines a flat and unpatterned top surface22 of the wafer 10 that makes for a good annealing surface.

The device side 12 a of the wafer 10 must remain at relatively lowtemperatures (an in particular below the melt temperature ofmetallization features 34) to protect the ultimate functionality of theCMOS device. The maximum temperature at the device side 12 a isdetermined by the particular metals used for the metallization features34, but is typically around 900° C. for copper interconnects and 600° C.for aluminum interconnects.

The constraint that the device features at the device side 12 a need toremain below the metallization melt temperature gives rise to therequirement that the laser thermal annealing time must be short enoughso that the device surface does not become too hot. This implies thatthe thermal annealing time (dwell time) must be such that thecorresponding thermal diffusion length L_(DIFF) must be less than thethickness TH of the device wafer 10 a.

For example, if the nominal thickness TH of the device wafer 10 a is 10microns, then the corresponding thermal annealing (dwell) time must beless than 10 μs based on the thermal diffusion length L_(DIFF) in bulksilicon for a 10 μs laser pulse being approximately 10 μs.Unfortunately, achieving such short dwell times t_(D) is not consistentwith the fundamental architecture for conventional laser annealing toolsthat utilize a 1-10 mm long, ˜100 micron wide laser line image that isscanned at ˜100 mm/sec.

Aspects of the disclosure are thus directed to a single-beam or adual-beam laser annealing system that can be used for both melt andsub-melt laser annealing applications. The dwell time t_(D) of theannealing beam is between 1 μs and 100 μs. In addition, a lasertemperature control system is optionally used to keep the annealingtemperature T_(A) substantially constant, i.e., to within an averagewafer surface temperature T_(S) of +/−3° C.

As discussed above, some semiconductor device manufacturing applicationswould benefit from having a laser annealing process with a dwell timet_(D) (annealing time t_(A)) of 100 μs or smaller, such as in the rangefrom 1 μs to 100 μs. It is desired that the thermal diffusion lengthL_(DIFF) associated the annealing time t_(A) be less than a physicaldimension of the wafer 10, for example the thickness TH of the devicewafer 10 a.

It is noted here that while the systems and methods disclosed hereinhave particular applicability to the product wafers 10 formed asdescribed above from a relatively thick carrier wafer 10 b that supportsa relatively thin device wafer 10 a, the systems and methods are alsoapplicable to laser annealing of conventional “thick” semiconductorwafers in situations where it is desirable to limit the amount ofdiffusion. An example of such a situation is the formation of shallowsource and drains in forming transistors, such as described in U.S. Pat.No. 6,365,476, U.S. Pat. No. 6,380,044 and U.S. Pat. No. 6,747,245. Inthe discussion below, the top surface 22 is the surface of wafer 10 thatis being annealed and can either be the “front side” of a conventionalwafer or the “back side” 14 a of the above-described product wafer 10.

FIG. 2 is a plot of the annealing time t_(A) (μs) versus the thermaldiffusion length L_(DIFF) (μm) for bulk silicon. From the plot, it canbe seen that for L_(DIFF)=10 μm, the corresponding annealing timet_(A)≈10 μs, while for L_(DIFF)=30 μm, t_(A)≈100 μs. For the productwafers 10 having a device wafer thicknesses TH about the same as thesethermal diffusion lengths L_(DIFF), one can see that the annealing timest_(A) have to be correspondingly small.

There is also the additional requirement that the optical absorptiondepth D_(AD) of the laser annealing beam into the wafer 10 be less thanthe thermal diffusion length L_(DIFF). FIG. 3 plots the opticalabsorption depth D_(AD) versus the wafer surface temperature T_(S) forwavelengths λ=1.06 μm, 0.98 μm and 0.53 μm. The plot of FIG. 3 indicatesthat for a device wafer thickness TH≈10 μm and at a relatively lowtemperature (e.g., 280° C. or below), one can use a laser with awavelength λ≈500 nm since the thermal diffusion length L_(DIFF) for thiswavelength is less than the device wafer thickness TH, while the otherwavelengths have thermal diffusion lengths L_(DIFF) that are greaterthan the device wafer thickness TH. For the device wafer thicknesses THin the range from about 50 μm to about 100 μm, a laser with a wavelengthλ≈980 nm can be used. Notice that for higher wafer surface temperaturesT_(S), the optical absorption depth D_(AD) shortens and thermaldiffusion becomes the dominant heat distribution mechanism.

From the plots of FIGS. 2 and 3, it is determined that for productwafers 10 formed using relatively thin device wafers 10 a, it isdesirable to use ultra-short annealing times and annealing wavelengthswhose optical absorption depths D_(AD) match the desired thermaldiffusion lengths L_(DIFF).

Dual-Beam Ultra-Fast Annealing System

For a given product wafer 10 having a particular device wafer thicknessTH, one can optimize the laser annealing system at a single wavelength.For example, in an image sensor fabrication application where the devicewafer thickness TH is on the order of 10 microns to 30 microns, one canselect a dwell time t_(D) of 10 microseconds and a 532 nm laserwavelength. For fabricating power devices, where the device waferthickness TH is approximately 50 microns, one can select a dwell timet_(D) of 25 microseconds and a longer wavelength laser. Examples ofultra-fast single-laser annealing are described below.

However, by combining two laser beams that use different wavelengths,the laser annealing system becomes more versatile. For example, in oneembodiment of a dual-beam laser annealing system described herein, onelaser beam can have a relatively short wavelength that enablesabsorption by a second laser beam having a relatively long wavelength.

FIG. 4 is a schematic diagram of an example dual-beam ultra-fast laserannealing system (“system”) 100. The system 100 includes a chuck 110having an upper surface 112 that supports the wafer 10. The chuck 110 inturn is operably supported by a wafer stage 116, which in an example istranslatable and rotatable, i.e., is movable in all three orthogonaldimensions and as well as in three orthogonal rotational directions toposition the wafer 10 as needed.

The system 100 also includes a primary laser system 120 that includes aprimary laser 121 that generates an initial primary laser beam 122 and asecondary laser system 150 having a secondary laser 151 that generatesan initial secondary laser beam 152. The primary laser system 120includes a primary optical system (“optics”) 130 configured to receivethe initial primary laser beam 122 and form therefrom a primary laserbeam 132. In an example, the primary optical system 130 includes ascanning optical system. Likewise, the secondary laser system 150includes a secondary optical system (“optics”) 160 configured to receivethe initial secondary laser beam 152 and form therefrom a secondarylaser beam 162. The secondary optical system 160 is configured as ascanning optical system and so is referred to hereinafter as scanningoptical system 160.

Example primary optical systems 130 and scanning optical systems 160 caninclude lenses, mirrors, apertures, filters, active optical elements(e.g., variable attenuators, etc.) and combinations thereof. In anexample, one or both of the primary optical system 130 and the scanningoptical system 160 are configured to perform beam conditioning, e.g.,uniformized their respective laser beams 132 and 162 and/or provide thelaser beams 132 and 162 with a select cross-sectional shape. Exampleoptical systems suitable for performing such beam conditioning aredisclosed in U.S. Pat. Nos. 7,514,305, 7,494,942, 7,399,945 and6,366,308, and U.S. patent application Ser. No. 12/800,203.

The primary and secondary laser beams 132 and 162 have respectivewavelengths λ₁ and λ₂ that in one example are both capable of heatingthe wafer 10 under select conditions. In another example, one wavelength(say, λ₁) is used to enhance the wafer 10 heating of the otherwavelength (λ₂). For example, one of the wavelengths λ₁ or λ₂ can havinga bandgap energy greater than the semiconductor bandgap energy of thewafer 10, thereby causing the wafer 10 to absorb primary and secondarylaser beams 132 and 162 to a degree sufficient to heat the wafer 10 toannealing temperatures T_(A). An example range for λ₂ is 500 nm to 10.6microns.

The system 100 also includes a thermal emission detector system 180arranged and configured to measure an amount of thermal emissionradiation 182 from the top surface 22 of the wafer 10 as described belowand generate an electrical thermal emission signal SE. In an example,the thermal emission detector system 180 measures emissivity E from thetop surface 22 of the wafer 10 and the electrical thermal emissionsignal SE is representative of the measured emissivity. In an example,the thermal emission detector system 180 utilizes at least a portion ofthe secondary laser system 150 so that it can track the scannedsecondary image 166, as discussed below.

In an example embodiment, the thermal emission detector system 180 andthe scanning optical system 160 have respective optical path sectionsOP_(E) and OP_(S) that overlap. This configuration enables the thermalemission detector system 180 to collect thermal emission radiation 182from the location of the secondary image 166 (introduced and discussedbelow) even while the secondary image 166 is scanning over the topsurface 22 of the wafer 10.

The system 100 also includes a collection optical system 200 used tocollect and detect a reflected light 162R from the top surface 22 of thewafer 10 and generate an electrical signal SR (“reflected light signal”)representative of the amount of detected reflected light 162R.

In an example embodiment, the system 100 further includes a controller170 electrically connected to the wafer stage 116 and is configured tocontrol the movement of the wafer stage 116 via instructions from thecontroller 170 as provided by a stage control signal S0.

In an example embodiment, the controller 170 is or includes a computer,such as a personal computer or workstation. The controller 170preferably includes any of a number of commercially availablemicro-processors, a suitable bus architecture to connect the processorto a memory device, such as a hard disk drive, and suitable input andoutput devices (e.g., a keyboard and a display, respectively). Thecontroller 170 can be programmed via instructions (software) embodied ina computer-readable medium (e.g., memory, processor or both) that causethe controller 170 to carry out the various functions of system 100 toeffectuate annealing of the wafer 10.

The controller 170 is also operably connected to the primary lasersystem 120 and the secondary laser system 150 and controls the operationof these laser systems 120 and 150 via respective control signals S1 andS2. In an example, the controller 170 includes digital signal processors(DSPs) (not shown) to control scanning functions in the primary andsecondary laser systems 120 and 150. The controller 170 is also operablyconnected to the thermal emission detector system 180 and the collectionoptical system 200 and is configured to receive and process theelectrical thermal emission signal SE and reflected light signal SR asdescribed below.

With continuing reference to FIG. 4, the primary laser beam 132 isdirected onto the top surface 22 of the wafer 10 to form a primary image136 thereon, while the secondary laser beam 162 forms a secondary image166, wherein the secondary image 166 falls within the primary image 136.An example of this configuration is illustrated in the close-up viewFIG. 5A that shows the primary and secondary images 136 and 166. Thesecondary image 166 is scanned over the top surface 22 of the wafer 10,as indicated by arrow AR2. The primary image 136 can be stationary andrelatively large, with the secondary image 166 scanned at leastpartially within. In another example embodiment illustrated in FIG. 5B,the primary image 136 can be relatively small and can be scanned, asindicated by arrow AR1, to keep up with scanned secondary image 166, asindicated by arrow AR2.

In another example embodiment shown in FIG. 5C through FIG. 5E, theprimary image 136 can extend over the entire scan path 167 of thesecondary image 166 so that the secondary image 166 can be scanned fromone edge of the wafer 10 to the opposite edge while still residingwithin the primary image 136, which in this case can be stationary. Thissituation can be maintained even when the wafer 10 is translated to movethe scan path 167 to a different portion of the top surface 22 of thewafer 10, as illustrated in FIGS. 5C and 5D, wherein in FIG. 5D thewafer 10 has been translated in the −Y direction so that the new scanpath 167 is on the lower part of the wafer 10 in FIG. 5D as compared tothe middle part of the wafer 10 in FIG. 5C.

As illustrated in FIG. 5B, the primary image 136 has a length L1 and awidth W1 while the secondary image has a length L2 and a width W2,though the primary and secondary images 136 and 166 need not berectangular. Example dimensions of the primary image 136 and secondaryimage 166 can be approximately 25 μm to 100 μm in width and 500 μm to2000 μm in length, consistent with the condition that the secondaryimage 166 falls at least partially within the primary image 136.

In an example embodiment, the primary and secondary laser beams 132 and162 have substantially Gaussian intensity profiles, so that the primaryand secondary images 136 and 166 also have substantially Gaussianintensity profiles in the X and Y directions. Allowing the primary andsecondary laser beams 132 and 162 to be substantially Gaussiansimplifies the configurations for the primary and secondary lasersystems 120 and 150, as compared to systems designed to form moresquare-wave (i.e., sharp-edged) intensity profiles.

In example embodiment, the primary image 136 can be slightly larger thanthe secondary image 166, or is substantially the same size. In anexample, the primary image 136 extends ahead of the secondary image 166in the scanning direction so that it can sufficiently heat the topsurface 22 of the wafer 10 so that the light in the secondary image 166is more readily absorbed by the top surface 22 of the wafer 10.

Prior art laser annealing systems effectuate scanning by moving waferstage 116, which can provide scanning speeds of about 100 mm/s. However,in the system 100, at least one of the primary and secondary lasersystems 120 and 150 are scanning optical systems that allow for rapidlyscanning at least one of the primary and secondary laser beams 132 and162 across the top surface 22 of the wafer 10. In an example, one orboth primary and secondary laser beams 132 and 162 are configured toscan their respective primary and secondary images 136 and 166 over thetop surface 22 of the wafer 10 at a scanning speed V_(S) that is in therange from about 5 m/s to about 25 m/s. For a scanning speed V_(S) of 25m/s, and a beam width of 25 μm, the dwell time t_(D) for the annealingprocess is 1 μs. For a scanning speed V_(S)=10 m/s and a beam width of50 μm, the dwell time t_(D)=5 μs. To transverse a 300-mm wafer 10, abeam moving at 10 m/s would need 30 ms, which relatively speaking is avery short scanning time.

During the scan of primary and secondary laser beams 132 and 162, thethermal emission detector system 180 monitors the thermal emissionradiation 182 from the location where the primary and secondary images136 and 166 overlap and heat the top surface 22 of the wafer 10. Thethermal emission detector system 180 generates the electrical thermalemission signal SE representative of the detected thermal emission andsends this electrical thermal emission signal SE to the controller 170.The controller 170 receives the electrical thermal emission signal SEand uses this electrical thermal emission signal SE to create afeed-back loop that controls the amount of power generated by at leastone of the primary and secondary laser systems 120 and 150 to controlthe laser power so that the annealing temperature T_(A) at the topsurface 22 of the wafer 10 remains substantially constant.

After the secondary laser beam 162 and its corresponding secondary image166 has fully scanned from one side of the wafer 10 to the other, thecontroller 170 causes the wafer stage 116 (via the stage control signalS0) to move to scan an adjacent portion of top surface 22 of the wafer10. In an example, wafer 10 is moved by amount that is equal to about ⅛of the length of scanned secondary image 166 so that adjacent scan paths167 have substantial overlap to improve annealing uniformity. In anexample, the secondary image 166 has a length L2=1 mm long so that thewafer stage 116 moves the wafer 10 in the cross-scan direction by about125 μm. After the wafer stage 116 is so moved, the secondary laser beam162 scans the top surface 22 of the wafer 10 in the same direction asthe previous scan. In this way, the temperature history of each point onthe wafer 10 is substantially the same.

In an example where the secondary laser system 150 includes a scanningmirror (as described below), and assuming that such a scanning mirrorrequires the same amount of time to return to its initial position as ittook to scan the wafer 10, this will take an additional 30 ms. Hence,the scanning mirror has an oscillation period of 60 ms, or anoscillation period of 16.67 Hz, which is well within the capability of aconventional scanning mirror system.

In an example, the wafer stage 116 is moved at a constant velocityrather than moving it in increments after each scan of the secondaryimage 166. In this embodiment, the wafer stage 116 can move 125 μm in 60ms, or 2.08 mm/sec. To fully anneal a 300-mm wafer would thus take 144seconds. For better uniformity, the secondary laser system 150 can beconfigured to turn off or block the secondary laser beam 162 betweenscans. This function can be accomplished using a modulator 198 disposedin the path of the secondary laser beam 162.

The amount of optical power needed for laser annealing is determined bythe required peak annealing temperature T_(AP) and the desired annealing(dwell) time t_(D). For longer annealing times (with subsequent largerthermal diffusion lengths L_(DIFF)), more volume of the wafer 10 isheated and so a larger amount of power is required. In an exampleembodiment, the peak annealing temperature T_(AP) is between 350° C. and1250° C. and is maintained to within +/−3° C. It is noted here that thepeak annealing temperature T_(AP) and the peak wafer surface temperatureT_(SP) are generally the same.

The throughput of the system 100 can be increases by increasing the size(i.e., length L2 and width W2) of the secondary image 166. To meet agiven annealing temperature requirement, a suitably powerful laser isrequired. It is estimated that 200 watts of absorbed laser power issufficient to raise the temperature of a 50 μm×1 mm area on the topsurface 22 of the wafer 10 by approximately 1000° C. when the annealing(dwell) time t_(D)≈5 μs. Hence, if the system 100 requires a throughputof sixty 300-mm wafers/hour and an annealing temperature T_(A) needs toreach the melting point of silicon (1413° C.), approximately onekilowatt of absorbed power is required.

One approach to achieving such a high amount of absorbed power is byproviding the secondary laser 151 in the form of a fiber laser. Thefiber lasers are very efficient, compact and can produce very good beamquality. The fiber lasers are most powerful in the wavelength range ofλ>1 μm, and can have outputs of multiple kilowatts in this range.Unfortunately, this wavelength range is not well absorbed by a siliconwafer at room temperature. However, a fiber-based secondary laser 151with λ>1 μm can be used in combination with a short-wavelength primarylaser 121 as pre-heat laser to initiate surface absorption. Therefore,in an example embodiment, the primary laser 121 generates a relativelyshort-wavelength primary laser beam 132 that is used to pre-heat orpre-activate the top surface 22 of the wafer 10 so that thelonger-wavelength secondary laser beam 162 is absorbed.

In an example embodiment, the primary laser 121 has a wavelength λ₁ inthe range from 300 nm to 650 nm. In an example, the primary laser 121includes a fiber laser that has an output wavelength in theaforementioned wavelength range for λ₁ and has an optical output in therange from about 50 watts to about 5000 watts. Other example the primarylasers 121 that can be used to pre-heat or pre-activate the top surface22 of the wafer 10 include CO₂ lasers, CW diode lasers and CW solidstate lasers. Preferably, the primary laser beam 132 is absorbed by thetop surface 22 of the wafer 10 at room temperature and the secondarylaser beam 162 is absorbed by the top surface 22 of the wafer 10 ateither room temperature or at the conditions created at the top surface22 of the wafer 10 by the primary laser beam 132.

FIG. 6 is another schematic diagram of an example system 100 thatincludes more details of an example thermal emission detector system180. The thermal emission detector system 180 includes a dichroic mirror184 that is configured (e.g., with coatings, not shown) to transmitlight of wavelength λ₂ associated with the secondary laser beam 162 butreflect light of other wavelengths, and in particular the wavelengthsassociated with the thermal emission radiation 182. The dichroic mirror184 defines an optical axis AD along which is arranged a polarizer 186,a focusing lens 188, an optional filter 190, and a photodetector 192.

In the operation of system 100 of FIG. 6, the thermal emission radiation182 is emitted by the top surface 22 of the wafer 10 in response tobeing heated by the primary and secondary images 136 and 166. Thethermal emission radiation 182 is collected by the scanning opticalsystem 160 and is directed to the dichroic mirror 184. The dichroicmirror 184 reflects the thermal emission radiation 182 down the opticalaxis AD to polarizer 186, which has the same polarization as thesecondary laser system 150. The polarized thermal emission radiation 182proceeds to the focusing lens 188, which focuses the thermal emissionradiation 182 on to photodetector 192. The optical filter 190 serves tofilter out extraneous wavelengths outside of the narrow wavelength bandΔλ_(E) associated with the thermal emission radiation 182. Here, anemission wavelength λ_(E) can be considered a center wavelength of thenarrow wavelength band Δλ_(E).

Thus the thermal emission radiation 182 is collected point by pointwhile the secondary image 166 is scanning over the top surface 22 of thewafer 10. In an example, the emission wavelength λ_(E) μs close towavelength λ₂ of the secondary laser beam 162 to keep aberrations towithin an acceptable tolerance. In an example the focusing lens 188 isconfigured to at least partially compensate for aberrations that arisefrom the scanning optical system 160 operating at the emissionwavelength λ_(E).

The thermal emission detector system 180 allows for the thermal emissionradiation 182 from the top surface 22 of the wafer 10 to be essentiallysimultaneously measure with the scanning of secondary image 166. Sincethe detection of thermal emission radiation 182 accomplished using afast photodetector 192, the corresponding thermal emission signal SE isessentially immediately available for closed-loop control of the amountof optical power in the secondary image 166. This improves the neededspeed for adjusting the amount of optical power in the secondary image166 to compensate for non-uniformities in the wafer surface temperatureT_(S). This is accomplished, for example, by adjusting the controlsignal S2 sent by the controller 170 to the secondary laser system 150.

To accurately control the temperature of the top surface 22 of the wafer10, one needs to be able to measure it accurately. The detection ofthermal emission radiation 182 as described above by itself does notprovide the wafer surface temperature T_(S). To measure the wafersurface temperature T_(S), the emissivity c must be measured. At a giventemperature, the emissivity ε depends on the emission wavelength λ_(E),the viewing angle, and the polarization of thermal emission radiation182. Systems and methods applicable to the present disclosure formeasuring the wafer surface temperature T_(S) by measuring theemissivity ε are described in U.S. Patent Pub. No. 2012/0100640.

One method of measuring the emissivity ε is to determine thereflectivity and transmission of the wafer 10 at the emission wavelengthλ_(E). This is accomplished by employing the secondary laser beam 162.If the wavelength λ₂ of secondary laser system 150 is above or close toSi absorption edge (i.e., about 1.1 μm), then the emissivity ε can bemeasured by measuring (or otherwise determining) the reflectivity andtransmissivity of secondary laser beam 162 incident upon the top surface22 of the wafer 10. However, where λ₂<1 μm or for λ₂>1 μm in combinationwith the high wafer surface temperatures T_(S) associated with laserannealing, the wafer transmissivity can be neglected and only ameasurement of wafer reflectivity is needed.

For the best accuracy, as much of the reflected light 162R from thesecondary laser beam 162 that reflects from the top surface 22 of thewafer 10 is collected. FIG. 7 is a close-up view of a collection opticalsystem 200 arranged to collect the reflected light 162R. The collectionoptical system 200 is shown arranged relative an scanning optical system160 that includes a scanning mirror 161M and a focusing lens 161L. Thecollection optical system 200 in incorporated into the system 100 and inan example includes along an axis A4 an integrating sphere 210 thatincludes an aperture 212. A photodetector 220 is arranged adjacent theaperture 212 to detect light that exits the integrating sphere 210 atthe aperture 212. In an example, at least one neutral density filter 216is disposed between the aperture 212 and the photodetector 220 tocontrol the intensity of light reaching the photodetector 220. Thephotodetector 220 generates the reflected light signal SR representativeof the power in the reflected light 162R collected by the integratingsphere 210 and provides this reflected light signal to the controller170.

With reference again to FIG. 6, in an example embodiment system 100includes a power sensor 250 configured to measure in real time theamount of power in the initial secondary laser beam 152, which allowsfor the amount of power incident upon the top surface 22 of the wafer 10to be determined.

In an example, the power sensor 250 is shown incorporated into thesecondary laser system 150. The power sensor 250 generates an electricalpower signal SPS (hereinafter, the emitted-power signal) representativeof the emitted laser power, which in the example shown in FIG. 6 isrepresentative of the power in the initial secondary laser beam 152. Thepower sensor 250 provides the emitted-power signal SPS to the controller170.

Note that the power sensor 250 can be located anywhere between secondarylaser 151 and the top surface 22 of the wafer 10. In the case shown inFIG. 6 where the power sensor 250 is located upstream of the scanningoptical system 160, the transmission of the scanning optical system 160needs to be accounted for in determining the amount of power in thesecondary laser beam 162 that is actually incident upon the top surface22 of the wafer 10. In particular, the transmission of scanning opticalsystem 160 can be provided to the controller 170 and used to calculatethe amount of power in the secondary laser beam 162.

The emitted-power signal SPS and the reflected light signal SR aremeasured in real time. By comparing these two signals SPS and SR(including any calculation regarding the transmission of scanningoptical system 160 as described above), the emissivity ε is calculatedon a point-by-point basis as the secondary image 166 scans over the topsurface 22 of the wafer 10. The calculated emissivity ε is then employedto obtain a local measurement of the wafer surface temperature T_(S),which is insensitive to emissivity variations due to any pattern presenton the top surface 22 of the wafer 10. This in turn allows forclosed-loop control of the amount of power in the secondary laser beam162 to form the secondary image 166 to achieve a substantially uniformannealing based on maintaining a substantially uniform the wafer surfacetemperature T_(S) (e.g., the peak wafer surface temperature T_(SP)). Inan example embodiment, the amount of power in the secondary laser beam162 is controlled by the controller 170 by sending a modulation signalSM to the modulator 198, which is disposed in the optical path betweenthe secondary laser 151 and the scanning optical system 160, e.g., ininitial secondary laser beam 152.

Thus, an aspect of the system 100 includes monitoring the peak wafersurface temperature T_(SP) of the top surface 22 of the wafer 10 duringannealing and adjusting the amount of power in the secondary laser beam162 so that the peak wafer surface temperature T_(SP) μs maintainedrelatively constant.

Scanning Optical System

FIGS. 8A through 8C are schematic diagrams of an example scanningoptical system 160 showing how the secondary laser beam 162 and thecorresponding secondary image 166 are scanned over the top surface 22 ofthe wafer 10. FIG. 9 shows the scanning optical system 160 from anotherview (direction) and shows how in one example scanning optical system160 is arranged so that the secondary laser beam 162 forms an angleθ_(B) with the surface normal N to the top surface 22 of the wafer 10,wherein θ_(B) is substantially the Brewster angle for silicon, which isabout 75°. The scanning optical system 160 has an optical axis AX2 thatis defined by the central light ray of the secondary laser beam 162.

FIGS. 8A through 8C and FIG. 9 can represent a single-laser annealingsystem such as shown in FIG. 10A, wherein the secondary laser system 150is the only laser system so that scanned secondary laser beam 162 is theonly annealing laser beam employed. In the single-laser-beam case, thelaser wavelength is one that is readily absorbed by the top surface 22of the wafer 10, e.g., λ₂ in the range from about 300 nm to about 650nm, or generally having a wavelength that does not require the topsurface 22 of the wafer 10 to be pre-heated or pre-treated byirradiation of another laser to facilitate absorption.

Alternatively FIGS. 8A through 8C and FIG. 9 can represent just one oftwo laser beams (see, e.g., FIG. 6), with the primary laser beam 132 notshow for ease of illustration.

The scanning optical system 160 includes the scanning mirror 161M andthe focusing lens 161L arranged to generally have an “F-Theta”configuration, though the secondary laser beam 162 need not betelecentric with respect to the top surface 22 of the wafer 10 over theentire scan path 167. The focusing lens 161L has an optical axis AXFL. Acollimating lens 161C is shown adjacent the secondary laser 151 andforms collimated initial secondary laser beam 152. The distance from thetop surface 22 of the wafer 10 to the focusing lens 161L is DW and thenumerical aperture of focusing lens 161L for the relatively narrowsecondary laser beam 162 is NA. An example distance DW is about 1 meterand an example NA is about 0.15. The scanning mirror 161M is operablyattached to a mirror driver 164, which in turn is operably connected tothe controller 170. The mirror driver 164 serves to drive the scanningmirror 161M, e.g., rapidly rotate the scanning mirror 161M through aselect angular range so that the secondary laser beam 162 can scan overa corresponding select angular range denoted in FIG. 8A as θ₂. In anexample, the angular range θ₂ is selected so that the secondary image166 can be scanned from one edge of the wafer 10 to the opposite edge atthe widest part of the wafer 10.

FIG. 8A shows the scanning optical system 160 in a state where thesecondary laser beam 162 forms the secondary image 166 on the topsurface 22 of the wafer 10 near one edge of the wafer 10, with thesecondary laser beam 162 being scanned in the direction indicated byarrow AR2. FIG. 8B is similar to FIG. 8A except that now the scanningmirror 161M has rotated so that the secondary laser beam 162 is directedalong the optical axis AXFL and the secondary image 166 is generallymid-way between the edges of wafer 10. FIG. 8C is similar to FIG. 8Aexcept that now the scanning mirror 161M has rotated even more so thatthe secondary laser beam 162 and the secondary image 166 has beenscanned over to the other side of wafer 10.

In an example, the scanning secondary laser beam 162 simply sweeps fromside to side while the wafer 10 is translated in the cross-scandirection so that the secondary image 166 exposes different portions ofthe top surface 22 of the wafer 10 on each scan, or at least covers somenew portion of the top surface 22 of the wafer 10 on adjacent scans(i.e., there can be some overlap of adjacent scans). Likewise, theprimary image 136 can be extend all along the scan path 167 and bestationary or can move along with the secondary image 166 so that theprimary image 136 pre-heats the portion of the top surface 22 of thewafer 10 to be scanned by the secondary image 166.

The system 100 can be employed for a variety of laser annealingapplications. For example, if a melt annealing process is desired, thesecondary laser beam 162 (as the annealing laser beam) can be used toheat the substrate to melt with a dwell time t_(D) of about 1 μs. If asub-melt annealing application is desired, the system 100 can beoperated so that the dwell time t_(D) μs in the range from about 1 μs toabout 100 μs. Both of these types of annealing applications benefit fromthe in-situ temperature measurement capability of the system 100.

Photoresist Annealing

The system 100 can also be employed to anneal photoresist, particularEUV photoresist used at nominal exposure wavelength of 13.5 nm and DUVphotoresist used at a nominal exposure wavelength of 193 nm. FIG. 10B issimilar to FIG. 10A and illustrates an example embodiment wherein thewafer 10 includes a EUV or DUV photoresist layer 27 on the top surface22 of the wafer 10. In this example, the photoresist layer 27 is thelayer to be annealed and wafer surface simply supports the photoresistlayer 27.

It has been shown that laser annealing can improve the performance ofEUV and DUV photoresist layer 27 in term of both sensitivity to theexposure light and line-edge roughness. However, a key to achieving thisimproved performance is the temperature uniformity of the annealing.Because the system 100 is configured to control the uniformity of theannealing temperature T_(A) using the above-described feedback loop, itenables the laser annealing of photoresist. This application may findparticular use in annealing photoresist used in extreme ultraviolet(EUV) lithography, where the increased photosensitivity of the resistcan reduce the amount of EUV power needed to expose the photoresist.Thus, an aspect of the disclosure includes performing ultrafast laserannealing using the system 100 as described above on a wafer 10 havingthe photoresist layer 27.

With photoresist annealing, the annealing secondary laser beam 162 istransmitted by the photoresist layer 27 because the photoresist layer 27is transparent to the annealing wavelengths. Thus, the photoresist layer27 is annealed by heating the underlying top surface 22 of the wafer 10.The annealing temperatures T_(A) for the photoresist layer 27 are in therange from about 300° C. to about 400° C., and the dwell times t_(D) arebetween 100 μs to 1 ms.

A main consideration in annealing the photoresist layer 27 is tosubstantially match the desired thermal diffusion length L_(DIFF) (for agiven dwell time t_(D)) to the optical absorption depth D_(AD) of lightin the underlying silicon wafer 10 because of the thermal diffusionlength L_(DIFF). In an example, a condition for laser annealing of thephotoresist layer 27 is that the optical absorption distance D_(AD) μsthan the thermal diffusion length L_(DIFF) (i.e., D_(AD)<L_(DIFF)).

For a dwell time of t_(D)=1 ms, FIG. 2 indicates that the thermaldiffusion length L_(DIFF) is roughly 100 microns. Hence, it is desirableto select one or more annealing wavelengths where the optical absorptiondepth D_(AD) is 100 microns or less. From FIG. 3, it can be seen thatthis condition is met for annealing wavelengths less than 980 nm at roomtemperature. For shorter dwell times (i.e., such as a dwell timet_(D)=10 μs), the thermal diffusion length L_(DIFF)=10 μm. Thecorresponding wavelength with an optical absorption depth D_(AD) lessthan 10 μm is a wavelength less than about 650 nm. An example annealingwavelength is in the range from about 300 nm to about 1000 nm. In anexample, the temperature measurement capability and feedbackconfiguration described above is utilized in the system 100 to controlthe temperature uniformity of the photoresist annealing process.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present disclosurewithout departing from the spirit and scope of the disclosure. Thus itis intended that the present disclosure cover the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An ultra-fast laser annealing system forannealing a semiconductor wafer having a wafer surface, comprising: aprimary laser system that forms a primary image on the wafer surface ata first wavelength, wherein the primary image increases an amount ofabsorption of light at a second wavelength; a secondary laser systemthat forms a secondary image on the wafer surface at the secondwavelength, wherein the secondary image resides at least partiallywithin the primary image; and wherein the secondary laser systemincludes a scanning optical system that scans the secondary image overthe wafer surface to define a scan path, wherein the secondary image hasa dwell time of between 1 μs and 100 μs, thereby causing the wafersurface to reach a peak annealing temperature T_(AP) between 350° C. and1250° C.
 2. The ultra-fast laser annealing system of claim 1, furthercomprising: a thermal emission detector system operably arranged todetect thermal emission radiation from the wafer surface at the locationof the secondary image and generate a first electrical signal; acollection optical system operably arranged to collect reflected lightfrom the secondary laser beam that reflects from the wafer surface atthe location of the secondary image and generate a second electricalsignal; a power sensor arranged to measure an amount of power in thesecondary laser beam and generate a third electrical signal thereof; acontroller operably connected to the thermal emission detector system,the collection optical system, the power sensor and the secondary lasersystem, the controller configured to receive and process the first,second and third electrical signals and determine therefrom wafersurface temperature T_(S) at the location of the secondary image.
 3. Theultra-fast laser annealing system of claim 2, wherein the thermalemission detector system and the scanning optical system includeoverlapping optical path sections.
 4. The ultra-fast laser annealingsystem of claim 2, wherein the controller is configured to control anamount of power in the secondary laser beam based on the determinedwafer surface temperature T_(S).
 5. The ultra-fast laser annealingsystem of claim 4, wherein the primary and secondary images generate apeak annealing temperature that does not vary over the semiconductorwafer by more than +/−3° C.
 6. The ultra-fast laser annealing system ofclaim 2, wherein the scanning optical system includes a scanning mirroroperably connected to a mirror driver, wherein the mirror driver isoperably connected to and controlled by the controller.
 7. Theultra-fast laser annealing system of claim 1, wherein the firstwavelength is in the range from 300 nm to 650 nm.
 8. The ultra-fastlaser annealing system of claim 1, wherein the second wavelength is inthe range from 500 nm to 10.6 microns.
 9. The ultra-fast laser annealingsystem of claim 1, wherein the secondary laser system includes a fiberlaser having an output power of between 50 watts and 5000 watts.
 10. Theultra-fast laser annealing system of claim 1, wherein the semiconductorwafer includes a device wafer having thickness in a range: a) from 10 μmto 100 μm, or b) from 500 μm to 1,000 μm.
 11. The ultra-fast laserannealing system of claim 1, wherein the primary image remainsstationary.
 12. The ultra-fast laser annealing system of claim 1,wherein the secondary image falls entirely within the primary image. 13.The ultra-fast laser annealing system of claim 1, wherein the wafer hasopposite edges and wherein the primary image extends between theopposite wafer edges.
 14. The ultra-fast laser annealing system of claim1, wherein the secondary image defines a line image.
 15. The ultra-fastlaser annealing system of claim 1, wherein the secondary image has awidth in the range from 25 μm to 100 μm and a length in the range from500 μm to 2000 μm.
 16. The ultra-fast laser annealing system of claim 1,wherein the semiconductor wafer has a device surface and an oppositeunpatterned surface, wherein the device surface supports device featureshaving a melt temperature and the unpatterned surface defines the wafersurface, the method further comprising: maintaining the device surfaceof the product wafer at a temperature below the melt temperature of thedevice features.
 17. An ultra-fast laser annealing system for annealinga product wafer that includes a device wafer having a device side thatsupports device features having a melt temperature and an oppositeunpatterned side that defines an annealing surface, the systemcomprising: a laser that generates a laser beam having an annealingwavelength in the range from about 300 nm to about 650 nm; a scanningoptical system that receives the laser beam and scans the laser beamover the annealing surface as a scanned image having a dwell time ofbetween 1 μs and 100 μs, thereby causing the annealing surface to reacha peak annealing temperature T_(AP) between 350° C. and 1250° C. whilemaintaining the device side of the product wafer a temperature below themelt temperature of the device features.
 18. The ultra-fast laserannealing system of claim 17, wherein the device wafer has a thicknessin the range from about 10 μm to about 100 μm.
 19. The ultra-fast laserannealing system of claim 17, wherein the scanning optical system isconfigured as an F-theta scanning system.
 20. The ultra-fast laserannealing system of claim 17, wherein the device features comprise atleast one of: CMOS features, aluminum interconnects and copperinterconnects.
 21. The ultra-fast laser annealing system of claim 17,wherein the device surface and the unpatterned surface define athickness between 500 μm and 1000 μm.
 22. The ultra-fast laser annealingsystem of claim 17, wherein the unpatterned surface includes anion-implant layer, and wherein the scanning of the secondary imagecauses the ion-implant layer to become conducting.